Inner Mongolia vs mainland China

Inner Mongolia and mainland China both are nouns.

Word	Noun	Adjective	Verb	Adverb
Inner Mongolia	Yes	No	No	No
mainland China	Yes	No	No	No

Inner Mongolia (noun)	mainland China (noun)
an autonomous region of northeastern China that was annexed by the Manchu rulers in 1635 and became an integral part of China in 1911	a communist nation that covers a vast territory in eastern Asia; the most populous country in the world